ifi'2 



13. Tlie bad agreement existing between the übservations ofWoHLKR 

 and liis co-workers and onr own, made us doubt for a moment 

 whether our a|>paratns arrangement might be the cause of the diffe- 

 rences. For a small quantity of SO, was deposited in the capillary 

 which connected the reaction tube with the manometer. Theoreti- 

 cally, it is very improbable that this phenomenon can have any 

 inllnence on the equilibrium pressure, for as soon as SO, disappears 

 from the gas mixture which is in contact with the solid substance 

 in the reaction tube, dissociation will again set in, until the original 

 SOj-pressure has again been attained. Only in those parts of the 

 apparatus where there is no longer any contact between gas and 

 solid substance and where moreover the teiuperature is low enough, 

 in other words in the capillary, a permanent decrease of the SO,- 

 tension can take place. Here, then forms a gas mixture of SO, and 

 , which plays the same role as the interlinked air cushion in the 

 measurements of Wöhler and co-workers. Our gas mixture, however, 

 is not inditferent but can on cooling, be reabsorbed coiuplelely by 

 the solid substance. Tt was, in fact, always observed that after heating 

 at a higher temperature follovv'ed by cooling, the equilibrium pressure 



12;. ^, CuSO^ tCu^O ^ SCuOCvtSO^ + SO^ 

 2:. CuOCuSO^ + Cu^O ^ 3C<xO + SO^ 

 SL. ZCuSO^^ CuOCuSO^ + SO3 . 

 VTT- atOCuSO^ ^ ZCuO + SO3 . 



